This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The purpose of this randomized, double-blind, cross-over study is to evaluate the beneficial effects of mexiletine 200mg three times a day in the tratment of NDM patients.